1. Field of the Invention
The present invention relates to a surface treating agent for an aluminum line pattern substrate and more particularly to a surface treating agent comprising an aqueous solution of quaternary ammonium hydroxide and sugar or sugar alcohol, which prevents after-corrosion of an aluminum pattern on a semiconductor substrate, i.e., corrosion of the aluminum pattern due to chlorine.
2. Description of the Related Arts
Heretofore, aluminum has been widely used as a material to form an electrode or a line pattern on a semiconductor substrate. In etching for the formation of the electrode or the line pattern, wet etching method using an acid or an inorganic alkali as a main component is employed. In addition, an etching method using an aqueous organic alkali solution, such as an aqueous solution of trimethyl(2-hydroxyethyl)ammonium hydroxide or an aqueous solution of tetramethylammonium hydroxide, is known (for example, Japanese Patent Publication Nos. 41529/1980 and 53211/1981, and Japanese Patent Application Laid-Open No. 161929/1980). However, etching for the formation of a pattern which is greatly increased in fineness is difficult to attain by the wet etching method, and in the case of the aqueous organic alkali solution, a rate of etching is too fast. For these reasons, in an etching process for the formation of a fine pattern, not the wet etching method but a dry etching method has been mainly employed in recent years. In this dry etching method, chlorine is mainly used as a chemical. This chlorine, however, causes the problem that it remains in a pattern substrate after etching and reacts with moisture in the air to thereby form a chlorine compound such as hydrochloric acid, which reacts with aluminum to cause corrosion of the aluminum (which is called "after-corrosion") and thus to reduce the fidelity of the semiconductor itself. In order to avoid the problem of aluminum corrosion due to the residual chlorine, various attempts have been made. For example, (1) a method in which after etching, the aluminum pattern substrate is heated to remove the residual chlorine, (2) a method in which after etching, heated nitrogen gas is blown onto the aluminum pattern substrate to remove the residual chloride, and (3) a method in which after etching, the aluminum pattern substrate is rinsed with pure water are proposed. In accordance with these methods, however, it is difficult to completely remove the chlorine remaining on the aluminum pattern substrate. In addition, (4) a method is known in which after etching, the aluminum pattern substrate is treated with fluorine- or oxygen-based plasma gas to form a passivation film on the surface of the aluminum pattern substrate, so that the surface of the aluminum pattern substrate is prevented from coming into contact with moisture and the aluminum corrosion is avoided. This method, however, fails to completely remove the chlorine responsible for the corrosion although the surface of the aluminum pattern substrate can be prevented from coming into contact with moisture. In a long term, therefore, it is not possible to completely prevent the formation of corrosion due to chlorine; it has been desired to completely remove the residual chlorine.
In view of these circumstances, the present inventors made extensive investigations on a treating solution for the aluminum pattern substrate after dry etching using chlorine. Since it is known that chlorine or chlorine compounds can be removed by treating with an alkali, it was attempted to use an aqueous organic alkali solution as described above, which has heretofore been used as an etching agent, for the purpose of removing chlorine. It has been found, however, that the aqueous organic alkali solution cannot be used for removal of the residual chlorine as it is, because it causes vigorous etching of aluminum.
As a result of further investigations, it has been found that an aqueous solution prepared by compounding sugar or sugar alcohol to an aqueous organic alkali solution containing a quaternary ammonium hydroxide represented by the general formula as described hereafter is very effective in preventing the etching of aluminum and in removing chlorine and other impurities.